Furnace launder construction



Jan. 18, 1944. P M, L E I 2,339,337

FURNACE LAUNDER CONSTRUCTION Filed March 14, 1942 2 Sheeis-SheetlINVENTOR PHILIP M. HULME ATTORN Y5 Filed March 14, 1942 2 Sheets-Sheet 2am wm mm 5 INVENTOR PHI IP M. HULME BY mm} PM ATTOR EYS Patented Jan.18, 1944 FURNACE LAUNDER CONSTRUCTION Philip M. Hulme, Metuchen, N. 1.,asslgnor to International Smelting and Refining Company, a corporationof Montana Application March 14, 1942, Serial No. 434,741

11 Claims.

This invention relates to furnace launder construction, and has for itsprincipal object to provide an improved form of launder heated bycombustion gases so as to permit the passage therethrough of a thin,easily frozen stream of molten metal. The invention further provides alaunder of improved construction such that the molten metal ismaintained out of contact with the combustion gases, and thusvcontamination of the molten metal by the combustion gases is prevented.

Launders for furnaces quite commonly are simple open troughs throughwhich the molten metal runs from the furnace to the pouring ladle. Suchlaunders are quite satisfactory for ordinary purposes where the streamof metal flowing through the launder is fairly large and not very easilyfrozen, and where contact between the molten metal in the launder andthe atmosphere is not objectionable. Such a launder, however, cannot beused if the molten metal stream is very thin and easily frozen, or ifexposure of the molten metal to the air is objectionable.

In United States Patent No. 2,265,284, granted December 9, 1941, menapplication of Philip M. Hulme and Robert A. Ghelardi, and assigned tothe same assignee as this application, a novel process is described formelting copper in a fuelfired mufiie furnace substantially solely bymeans of radiant heat. The molten copper produced by this meltingprocess'is as free from contaminants as the solid copper charged intothe furnace. When electrolytic cathodes are used as the source of solidcopper to be melted, the molten copper product is very pure and issubtantially oxygen-free. If the substantially oxygen-free molten copperproduced in this manner is allowed to flow through an open launder, itrapidly picks up oxygen from the air, so that it is impossible to castthe metal into oxygen-free shapes. The present invention provides alaunder constructed so as to exclude air from contact with the moltencopper or other metal flowing therethrough, and hence suitable fortransferring oxygen-free copper melted as described in theaforementioned patent to the pouring apparatus.

The melting process described in the aforementioned patent is such thatit may be carried out continuously. When the melting process is thuscarried out, there is a continuously flowing stream of metal from thefurnace through the launder to the pouring ladle. This continuous streamof molten metal is, however, very thin and small, even in the case of afurnace having quite large melting capacity. The stream of copper is sothin that it is easily chilled and frozen, and when this occurs,continuous operation of the furnace is interrupted. The launder providedby the present invention is of such nature that the molten copper orother metal flowing therethrough is kept heated and so is prevented fromfreezing.

The launder according to the invention comprises an enclosed conduit forcarrying the thin stream of molten copper or other metal. Acombustion-gas chamber extends substantially the full length of theconduit, and is separated therefrom by a thin, substantially gas-tightwall of heat-conducting refractory material. Means are provided forintroducing hot combustion gases into the combustion-gas chamber incontact with the said wall. In this manner they wall may be heated to anelevated temperature above the melting point of the copper or othermetal flowing through the conduit, and thereby suflicient radiant heatmay be supplied to the flowing metal to maintain it in the moltencondition. At the same time, the wall maintains the molten metal out ofcontact with the combustion gases. If desired, arrangement may be madeto introduce a special protective gas atmosphere into the conduit inorder to insure against contamination of the molten metal.

A particularly satisfactory form of launder according to the inventioncomprises atrough of refractory material communicating with the meteriorof the furnace. A substantially gas-tight cover of heat-conductingrefractory material is laid over the trough, and a combustion-gaschamber extending substantially the full length of the trough isprovided above the cover. Hot combustion gases are introduced'into thecombustion-gas chamber, and thus into contact'with the cover, at one endof the combustion-gas chamber. Means are provided for withdrawing suchgases from the combustion chamber at the other end thereof.

The invention will be better understood from the following descriptionof a specific embodiment, considered in conjunction with theaccompanying drawings, in which Fig. 1 is a longitudinal section througha launder connecting ing ladle;

4 Fig. 2 is a horizontal section through the launder shown in Fig. 1,taken substantially along the line 2-2 of Fig. 1; and

Fig. 3 is a cross-section through the combustion chamber and launder,taken substantially along the line 3-3 of Fig. 2.

a mufile furnace with a pour-- ie- A combustion chamber 26 Referringparticularly to Fig. l, the launder l connects the melting chamber ll ofa mufiie furnace 12 with a pouring ladle l3. Neither the construction ofthe furnace l2 nor the construction of the pouring ladle l3 forms anypart of the present invention. However, the furnace shown is of the typedescribed and claimed in the co-pending application of Vernon E.MacDonell, Serial No. 434,709, filed March 14, 1942, and the pouringladle shown is of the type described and claimed in my co-pendingapplication Serial No. 434,742, filed March 14, 1942. The apparatusshown in the drawings is especally useful for carrying out the coppermelting process described in the aforementioned Patent No. 2,265,284.

Molten metal, such, for example, as oxygenfree molten copper, ismaintained in the melting chamber to a normal level L. The copper may bemelted and maintained in the molten state substantially wholly by meansof radiant heat radiated from an arch |4 separating the melting chamberII from a combustion chamber IS. The molten copper or other metal passesfrom the melting chamber |l through a well l6 and a tap hole into thelaunder.

The launder shown in the drawings comprises a steel supporting structurel8 suitably lined with refractory brickwork IS. A series of troughshapedrefractory brick or tile 20 are supported by the refractory brickwork l3to provide a trough or conduit 2| for the molten metal flowing from thefurnace. The trough 2| receives the molten copper from the tap hole l1,and delivers it to the interior of the pouring ladle l3 through the pipe|3a.

A substantially gas-tight cover 22 is laid over the open top of thetrough-shaped tiles to enclose the trough 2|. The cover 22 is preferablymade of a thin, heat-conducting refractory tile composed, for example,of silicon carbide. The cover 22 advantageously is substantially gastight so as to protect metal flowing through the trough 2| from contactwith any deleterious gases. If desired, a pipe 23 may be provided forintroducing a protective gas atmosphere into the trough 2| to insureagainst contamination of the molten metal. A protective gas composedessentially of carbon monoxide and nitrogen is particularly suitable forprotecting molten copper from contamination.

A combustion-gas chamber 24 is provided above the thin refractory troughcover 22, and is defined by refractory brickworkside walls 25 and roof25a arranged about the cover 22 but in spaced relationship therewith.The combustiongas chamber extends substantially the full length of thetrough 2|. The refractory side walls 25 of the combustion-gas chambermay be mounted permanently in place as lining for the steel shell l3,but the refractory brickwork 25a forming the roof of this chamber may besecured to removable steel plates 2512. Such construction facilitatesremoval of the combustion chamber roof for repairs to or inspection ofthe launder. Each of the plates 25b may be offset with respect to therefractory 25a attached thereto so as to overlap the refractory attachedto the adjacent plate and thus improve the gas-tightness of the jointsbetween adjacent refractory elements 25a and plates 2512. t,

(Figs. 2 and 3) is provided near the metal-discharge end of the launder.The combustion chamber is defined by refractory brickwork 21 lining asteel supporting shell 28, and is so arranged that it communicates withthe interior of the combustion-gas chamber 24. An oil burner 29 ismounted so as to face into the combustion chamber 26. An off-take flue30 (Fig. 2) communicates with the interior of the combustion-gas chamber24 adjacent the furnace end of the launder, and provides forthewithdrawal of combustion gases therefrom to a chimney 3|.

In operation of the launder described above, fuel introduced through theburner 29 is burned in the combustion chamber 26. The hot combustiongases thus formed pass into the combustion-gas chamber 24 and intocontact with the thin heat-conducting refractory cover 22 over thetrough 2|. temperature above the melting point of the copper (or othermetal) flowing through the trough. Consequently, heat is radiated fromthe inner surface of the cover to the fiowing stream of copper tomaintain it in the molten condition. Even very thin, easily frozenstreams of molten copper may thus be kept flowing continuously withouteven partially freezing during passage through the launder.

The arrangement for supplying the heat necessary for this purpose byradiation from the trough cover 22 achieves effective heating of thecopper by the relatively inexpensive process of burning a fuel, butwithout permitting the molten copper to be contaminated by thedeleterious prodnets of the fuel combustion.

As shown in the drawings, the combustion gases pass through thecombustion-gas chamber 24 in a direction countercurrent t0 the flow ofmolten copper through the trough 2|. The cover 22 over the troughthereby may be heated to its highest temperature adjacent the dischargeend of the trough, where the danger that a thin stream of molten coppermay freeze is greatest, and where, in the absence of an adequate supplyof heat, freezing ordinarily would take place.

The combustion gases, after passing through the combustion chamber 24,pass through the flue 30 and out the stack 3|. If desired, these gasesmay be passed through a waste heat boiler or other heat recuperatingmeans before they are allowed to escape into the atmosphere.

The substantially gas-tight cover 22 over the trough effectivelyseparates the molten copper flowing through the trough 2| from contactwith the combustion gases, and thereby protects the copper fromcontamination by the deleterious combustion products (such as carbondioxide and water vapor) present in these gases. Moreover,

5 the cover 22 serves to confine any inert or reducing protective gasatmosphere introduced into the trough 2| through the pipe 23 for thepurpose of providing additional protection to the molten copper.

In order to permit of observation of copper entering and flowing throughthe launder, windows or other appropriate observation ports 32 and 33may be provided. Advantageously one of the windows 32 i located at apoint to permit observation of the copper flowing through the tap holeI! into the launder, and another window 33 is arranged in the endclosure 34 at the end of the launder to permit observation of the thincopper stream flowing into the pouring ladle l3.

If it is desired to incorporate alloying ingredients, such as silicon orphosphorus, in the copper as it is withdrawn from the furnace throughthe launder, a hopper 35 providedwith a suitable valve mechanism 36 maybe provided adjacent the discharge end of the launder. A slug of phos-The cover 22 thereby is heated to a phorus-copper or silicon-coppermaster alloy. or

other alloying material, may then be dropped the ladle 13.

The launder herein described may be so connected to the iumace-that thepassage for the flow of copper into the launder is fully enclosed and issubstantially gas tight, as shown in the drawings. Hence, there is nodanger of contaminating gases entering the launder at this point. Thedischarge end of the launder is closed by the and closure structure 34in which the observation window 33 is mounted. The bottom of thesupporting steel shell It at the discharge end of the launder, and thebottom of the corresponding supporting steel shell of the and closur 34,may be curved cylindrically to mate with the cylindrical curvature ofthe pouring ladle, thus'permitting the ladle to tilt back and forth onits axis for pouring without creating any substantial aperture throughwhich air might gain access to the molten copper or other metal. A verysmall positive pressure of inert or reducing protective gas introducedthrough the pipe 23 will effectually prevent the entrance of air throughwhatever slight cracks or open seams may unavoidably be present in thestructure or at the junction between launder and pouring ladle. Thus thelaunder is such that molten substantially oxygenfree copper may betransferred from the melting furnace I2 to the pouring ladle IS withoutbecoming oxidized or otherwise contaminated.

Although particular reference has been made in the foregoing descriptionto the use of the new launder for transferring molten .copper from amelting furnace to a pouring ladle, it is understood that the laundermay be used for transferring other molten materials from one point toanother.

I claim:

1. A launder for conducting a thin stream of molten metal from afurnace, comprising a trough of refractory material communicating withthe interior of the furnace, a substantially gas-tight cover ofheat-conducting refractory material over said trough, a combustion-gaschamber immediately above said cover and extending substantially thefull length thereof, and means for introducing hot combustion gases intosaid combustion-gas chamber, whereby the cover over said trough may beheated and thus maintain a thin stream of metal flowing through thetrough in the molten condition by means of radiant heat.

2. A launder for conducting a thin stream of molten metal from afurnace, comprising a trough of refractory material communicating withthe interior of the furnace, a combustion-gas chamher over said troughand extending substantially the length thereof, a thin substantiallygas-tight cover of heat-conducting refractory material over said troughand separating it from said combustion-gas chamber, and means forintroducinghot combustion gases into said combustion-gas chamber,whereby said cover may be heated to an elevated temperature above themelting point of the metal flowing through the troughand may therebysupply sumcient radiant heat to said flowing metal to maintain it in themolten condition.

3. A launder for conducting a thin stream of molten metal from afurnace, comprising a trough of refractory material communicating withthe interior of the furnace, a combustion-gas chamber over said troughand extending ubstantially the length thereof, a thin substantiallygas-tight cover of heat-conducting refractory material over said troughand separating it from said combustion-gas chamber, means forintroducing hot combustion gases into said combustion chamber adjacentone end of the launder, and means for withdrawing said combustion gasesfrom said chamber adjacent the other end of the launder, whereby saidcover may be heated to an elevated temperature above the melting pointof the metal flowing through the trough and may thereby supplysufllcient radiant heat to said flowing metal ber adjacent themetal-discharge end of the 1aunder, and means for withdrawing thecombustion gases from said chamber adjacent the furnace end of thelaunder, whereby said trough cover may be heated to an elevatedtemperature above the melting point of the metal by the combustion gasesflowing countercurrent to the flow of molten metal through the troughand may thereby supply sufllcient radiant heat to said fiOWing metal tomaintain it in the molten condition.

5. A launder of the character described comprising an enclosed conduitfor carrying a thin stream of molten metal, a combustion-gas chamberextending substantially the length of said conduit, a thin substantiallygas-tight wall of heat-conducting refractory material separating saidcombustion-gas chamber from the interior of said conduit, and means forintroducing hot combustion gases into said chamber in contact moltenmetal from a furnace, comprising a, trough.

of refractory material communicating with the interior of the furnace, acombustion-gas chamber over said trough and extending substantially thelength thereof, a thin substantially gas-tight cover of heat-conductingrefractory material over said trough and separating it from saidcombustion-gas chamber, a combustion chamber communicating with saidcombustion-gas chamber adjacent one end thereof, a burner for producinghot combustion gases in said combustion chamber, and means adjacent theother end of the combustion-gas chamber for withdrawing combustion gasestherefrom after passing from the combustion chamber through saidcombustion-gas chamber in contact with said trough cover, whereby saidcover may be heated to an elevated temperstream of molten metal, acombustion-gas chamher extending substantially the length of saidconduit, a thin substantially gas-tight wall of heat-conductingrefractory material separating said combustion-gas chamber from theinterior of said conduit, means for introducing a protectlve gasatmosphere into said conduit, and means for introducing hot combustiongases into said chamber in contact with said wall, whereby said wall maybe heated to an elevated temperature above the melting point of thcmetal flowing through said conduit and may thereby supply sufilcientradiant heat to said flowing metal to maintain it in the moltencondition while the metal is maintained out of contact with thecombustion gases.

8. A launder for conducting a thin stream of molten metal from afurnace, comprising a trough of refractory material communicating withthe interior of the furnace, a combustiongas chamber over said troughand extending substantially the length thereof, a thin substantiallygas-tight cover of heat-conducting refractory material over said troughand separating it from said combustion-gas chamber, means forintroducing a protective gas atmosphere into said trough, and means forintroducing hot combustion gases into said combustion gas chamber,whereby said cover may be heated to an elevated temperature above themelting point of the metal flowing through the trough and may therebysup.- ply suflicient radiant heat to said flowing metal to maintain itin the molten condition.

9. A launder of the character described comprising an enclosedmetal-carrying conduit, the under side of said launder adjacent themetal discharge end thereof being curved substantially uniformly and in.such manner as to mate with a correspondingly curved tiltable ladle,whereby such ladle may be tilted without thereby creatinganysubstantlalapertureattheiimctnrewlththe launder.

10. A launder of the character described comprising an enclosedmetal-carrying conduit, the under side of said launder adjacent thedischarge end thereof being curved concavely and substantiallycylindrically, whereby said launder may be mated with a corrly curvedtiltable ladle and such ladle may be tilted without thereby creating anysubstantial aperture at the curved juncture with the launder.

11. A launder for conducting a thin stream of molten metal from a iumaceto a tiltable pouring ladle, comprising a trough of refractory materialcommunicating at one end with the interior of the furnace anddischarging at the other end into the pouring ladle, a substantiallygas-tight cover of heat-conducting refractory material over said trough,a combustion-gas chamber immediately above said cover and extendingsubstantially the full length thereof, and means for introducing hotcombustion gases into said combustion-gas chamber, whereby the coverover said trough may be heated and thus maintain a thin stream of metalflowing through the trough in the molten condition by means of radiantheat, while the molten metal itself is maintained out of contact withcontaminating combustion and other gases, the underside of said launderadjacent the discharge end being curved substantially uniformly and insuch manner as to mate with a correspondingly curved surface of thepouring ladle, whereby the ladle may be tilted without thereby creatingat its juncture with the launder any substantial aperture through whichcontaminating gases could pass in deleterious amounts into contact withthe molten metal in the launder.

PHILIPM. HULME.

